The present invention concerns a watch case whose constituent elements are secured to each other via the bezel. The invention more particularly concerns a watch case able to classified in the xe2x80x9cthree partxe2x80x9d category, i.e. a case including an independent bezel, middle part and back cover, which after assembly, delimit with the crystal a space in which a movement is housed allowing a digital or analogue time display on a dial arranged below the crystal.
In order to secure these three parts to each other, in very numerous devices already proposed, the middle part generally constitutes the essential element allowing the bezel and back cover to be secured by screws, being driven in, or by bonding.
It is for example possible to provide in the middle part, on one side a first series of holes for screwing in the bezel, and on the other side a second series of holes for screwing in the back cover, the movement or the casing ring containing the latter then being wedged on by suitable shoulders in the middle part.
In Swiss Patent No. 645 497, only a single series of holes is provided for accommodating a first screw used to secure the bezel and whose threaded head, embedded in the middle part allows a second screw to be screwed in to fix the back cover, the two screws having opposite pitch. This stacked assembly may lead one to believe that the bezel is the essential assembly element, but it is clear that the middle part is indispensable for closing the periphery of the case and for allowing a movement to be set in place.
The watch case disclosed in European Patent No. 0 443 366 is formed of two shells joined by a middle part, the lower shell forming a screwed on back cover and the upper shell in fact being a thin bonded crystal-bezel.
The watch case according to the present invention on the other hand allows an assembly to be obtained of the various constituent elements, without using the middle part as a mechanical connecting element. The middle part nonetheless keeps a functional role in particular for reinforcing sealing and for allowing the strands of a wristband to be secured. Since it has no mechanical function it can also be made more simply and economically, for example by moulding or plastic material injection moulding and thus allowing great freedom of choice as regards the different collection designs.
The invention thus concerns a watch case including a back cover, a middle part and a bezel closed by a crystal delimiting together a space in which a watch movement is housed supported by a plate and allowing an analogue or digital time display on a dial arranged below the crystal. The construction of this case is characterised in that the bezel forms the essential assembly element. In order to do this the bezel is made of metal and has locally a ring of sufficient thickness to allow series of blind holes to be made in its lower part. A first series of threaded holes is intended for screwing in a first series of screws for fixing the movement onto the bezel. A second series of threaded holes, offset angularly with respect to the first series, passing through the movement, is intended for screwing the back cover into the lower part of the bezel.
In order to have greater precision in positioning the movement, it is also possible also to provide in the bottom of the bezel two blind holes in which two pins, mounted on the movement, will engage.
The bezel, the movement and the back cover thus form a perfectly rigid unit which is not sensitive to shock waves capable of destabilising the fragile parts of the movement. It goes without saying that the assembly of these three elements is achieved by inserting the middle part which, since it no longer has an assembly function, can be loose between sealing gaskets provided in the region of the middle part and back cover and allow wristband strands to be secured.
In order to fix the movement and the back cover onto the bezel, facing the two series of threaded holes, holes are provided either in the plate supporting the elements of the movement, or in a casing ring of said plate.